The feral cat situation in our area of the UK is seemingly small until you talk to vets in the area. There is a very large feral cat population living on the plain, well away from human interference. As more houses are built closer and closer to the edge of the plain the feral cats are spreading disease to the pet population and any cat not vacinated is more or less a dead cat ( there are only a very few people in the UK who would consider having indoor cats).
In our cities - the problem is as bad as anywhere.
A long term study has been done on a group of feral cats in Rome and if a cat survives kittenhood and the traffic it can expect a life of roughly six to eight years there.